This invention relates generally to treatment of exhaust gas produced by an internal combustion engine, and particularly to an air control valve for controlling flow between an air pump and an exhaust gas treatment system in an automotive vehicle.
Certain operating modes of an internal combustion engine of an automotive vehicle may require the introduction of air directly into a catalytic exhaust gas treatment system to make the treatment as effective as possible. For example, introducing air at cold start may facilitate oxidizing hydrocarbons in the exhaust gas before the catalytic treatment is able to be fully effective. Such air is introduced under pressure into the exhaust gas stream ahead of a catalyst by an air pump that is powered in any appropriate manner, often electrically. The air that is introduced in this way is sometimes referred to as secondary air. It may be undesirable to connect certain air pumps directly to the exhaust gas stream, in which case such an air pump may be connected to the exhaust gas stream through a control valve. Such a valve should possess a predictable and rapid response.
It is toward providing such a valve that the present invention is directed.
A general aspect of the invention relates to an electric operated control valve for controlling fluid communication between an air pump and a gas treatment system that treats exhaust gas produced by an internal combustion engine.
Within this general aspect is the more specific aspect of the valve comprising a body having an inlet for communicating the valve to the air pump and an outlet for communicating the valve to the gas treatment system, an electric operator, and a reed that is disposed between the inlet and the outlet and that, during absence of a predetermined electric energization of the operator, is normally open to allow communication between the air pump and the gas treatment system but is forced closed in response to fluid pressure at the outlet exceeding fluid pressure at the inlet by more than a predetermined amount, and that during presence of the predetermined electric energization of the operator, is forced closed to disallow communication between the air pump and the gas treatment system.
Another aspect relates to the valve mechanism being controlled by the operator and by the difference between fluid pressure at the inlet and fluid pressure at the outlet. The mechanism allows communication between the air pump and the gas treatment system as long as fluid pressure at the outlet does not exceed fluid pressure at the inlet by more than a predetermined difference during absence of a predetermined electric energization of the operator, disallows communication between the air pump and the gas treatment system during presence of the predetermined electric energization of the operator, and disallows communication between the air pump and the gas treatment system whenever fluid pressure at the outlet exceeds fluid pressure at the inlet by more than the predetermined difference.
Still another aspect relates to a mechanism for such a valve where a reed that is normally open is electromagnetically coupled with the operator to operate from open to closed in response to the predetermined electric energization of the operator, and that during absence of the predetermined electric energization of the operator, operates from open to closed in response to fluid pressure at the outlet exceeding fluid pressure at the inlet by more than the predetermined difference.
Still another aspect relates to a method for controlling fluid communication between an air pump and a gas treatment system that treats exhaust gas produced by an internal combustion engine. The method comprises: allowing communication between the air pump and the gas treatment system as long as fluid pressure at the outlet does not exceed fluid pressure at the inlet by more than a predetermined difference during absence of a predetermined electric energization of an electric operator; disallowing communication between the air pump and the gas treatment system during presence of the predetermined electric energization of the operator; and disallowing communication between the air pump and the gas treatment system whenever fluid pressure at the outlet exceeds fluid pressure at the inlet by more than the predetermined difference.
The accompanying drawings, which are incorporated herein and constitute part of this specification, include one or more presently preferred embodiments of the invention, and together with a general description given above and a detailed description given below, serve to disclose principles of the invention in accordance with a best mode contemplated for carrying out the invention.